Seismic Activity in Japan August 1999

1 Major Seismic Activity

* Except for a Magnitude (M) 5.4 earthquake that occurred on 21 August in northern Wakayama Prefecture (Pref.), there was no marked activity; all was quiet.

• The whole of Japan M4 (August 1999)

2 Seismic Activity in each Region

(1) Hokkaido Region

* As was the case in July, there was no marked activity.

• Hokkaido Region

(2) Tohoku Region

* Since June there has been no marked activity.

• Tohoku Region

(3) Kanto-Chubu Region

* An M4.0 earthquake occurred on 11 August in Tokyo Bay at a depth of about 60km.

* The results of GPS observation in the Tokai (Shizuoka-Aichi-Gifu) area showed no marked variation. The results of Kakezawa-Omaezaki (Hamaoka) leveling showed no marked variation.

• Kanto-Chubu Region
• Seismic activity in Tokyo Bay
• GPS continuous observation base-line chart (the vicinity of Kakegawa and Omaezaki)
• Base-line-length variation graph
• Height-difference variation graph
• Secular variation of benchmark 2595 (Hamaoka Town)

(4) Kinki-Chugoku-Shikoku Region

* An M5.4 earthquake occurred on 21 August in northern Wakayama Pref. at a depth of about 70km, and a maximum intensity of 5 lower was recorded. The hypocenter was inside the subducting Philippine Sea Plate. Only several aftershocks were recorded.

• Kinki-Chugoku-Shikoku Region
• Seismic activity in northern Wakayama Pref.

(5) Kyushu-Okinawa Region

* There was no marked activity this month.

• Kyushu Region
• Okinawa Region